In certain instances it is desirable that rainwater and the like drain quickly from a surface area covered by paving tiles. In certain uses it is desirable that the water quickly drain through the pavers (in which case a high permeability is desired). In other instances it is desirable that the water be retained within the pavers and slowly released through drainage and/or evaporation. One example where this latter feature is desirable is in managing storm water. In this instance it can be further advantageous that the pavers provide a filtering function to remove particulate matter and other pollutants from the storm water. Since storm water typically is routed to sewer systems via storm drains, storm water and pollutants contained therein can place a significant burden on sewage treatment facilities. It is thus desirable to reduce the volume of storm water flowing into storm drains, and also to remove contaminates from the storm water before it enters the storm drains. It is further desirable that filler material (such as sand and gravel) beneath and between pavers and the like also be able to retain a large volume of water and release the water slowly. In addition to filtering storm water, it is also desirable to provide a durable porous material that can be used to filter air and other liquid and gas flows.
It is also desirable to be able to form unitized building materials (as for example, bricks, pavers, beams, unitized slabs and other building materials) having high strength, but that do not require significant amounts of cement in their formation. That is, it is desirable to reduce the amount of cement required in forming such unitized building materials. At least in the U.S., the Portland cement manufacturing industry is becoming increasingly regulated (e.g., by the U.S. Environmental Protection Agency at the U.S. Federal level) to reduce emissions of toxic air pollutants, such as mercury, acid gases, carbon dioxide, and total hydrocarbons, along with emissions of particulate matter, which are typically generated during the manufacture of cement.
It is additionally desirable to provide an alternative to clay-based bricks which combine structural and architectural elements, and which can be kilned in a time period shorter than the typical clay-based brick kilning period (commonly about 24-48 hours), thus reducing energy consumption and environmental pollutants (such as carbon dioxide) frequently associated with energy generation.
It is further desirable to provide unitized building materials, and in particular, such materials used in walkways and roadways, that are chemically resistant to ice melting chemicals and other materials that may be applied atop of the unitized building materials. Still further, in certain applications it is desirable that unitized building materials be light weight, yet still retain the strength required for their intended use. It is also desirable to achieve higher strengths (compressive and/or tensile) in unitized building materials, as well as increased resistance to stresses imposed by freezing and thawing of water that can be entrained within the unitized building materials.